Spring Boot 自动配置顺序 [英] Spring Boot AutoConfiguration Order
问题描述
我在使用 Spring Boot 在多模块 Maven 项目中以所需的顺序应用一些 Spring 配置时遇到了一些麻烦.
I am having some trouble getting some Spring configuration to be applied in the desired order with Spring Boot in a multi-module Maven project.
我有模块 A 和 B 由我编写，并且依赖于我在模块 C 中无法控制的第三方模块(依赖关系如下:A 依赖于 C，B 依赖于 A)
I have modules A and B that are written by me and a dependency on a third party module that I have no control over in module C (dependencies are as follows: A depends on C, B depends on A)
在模块 A 中，我有一个用 @Configuration 和 @AutoConfigureBefore(ClassFromModuleD.class) 注释的类.在模块 B 中，我有另一个用 @Configuration 和 @AutoConfigureBefore(ClassFromModuleA.class)
In module A I have a class annotated with @Configuration and also @AutoConfigureBefore(ClassFromModuleD.class). In module B I have another class annotated with @Configuration and also @AutoConfigureBefore(ClassFromModuleA.class)
我希望这会导致我的模块 B 中的 bean 定义首先被配置，然后是我的模块 A 配置类中的 bean，最后是 C 中的那些.
I was hoping that this would result in the bean definitions in my module B being configured first, followed by beans in my module A configuration class then finally the ones in C.
我还尝试向模块 A 和 B 中添加一个 META-INF/spring.factories 文件，该文件声明了存在于其自己模块中的单个配置文件.例如对于模块 A
I also tried adding a META-INF/spring.factories file to both module A and B which declares the single configuration file present in its own module. E.g. for module A
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.exmaple.moduleAConfiguration
在模块 B 中:
org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.exmaple.moduleBConfiguration
我没有看到想要的配置顺序，事实上，它似乎与我想要的完全相反.我使用了日志语句和调试器来逐步执行，似乎首先应用模块 C 中的配置，然后是 A，最后是 B.
I am not seeing the desired order of configuration, in fact, it seems to be the exact opposite to what I want. I have used logging statements and a debugger to step through and it seems the config from Module C is applied first, followed by A then finally B.
谁能指出我可能遗漏了什么，或者是否有其他方法可以做到这一点?非常感谢.
Could anyone point out what I may have missed or if there is another way to do this? thanks very much in advance.
推荐答案
Spring AutoConfiguration 用于提供基本配置，如果某些类是否在类路径中.
Spring AutoConfiguration is used to provide a basic configuration if certain classes are in the classpath or not.
这用于例如如果 Hibernate 在类路径上，则提供基本的 Jpa 配置.
This is used e.g. to provide a basic Jpa configuration if Hibernate is on the classpath.
如果要配置spring实例化bean的顺序可以使用
If you want to configure the order in which beans are instantiated by spring you can use
@DependsOn("A")
public class B{
...
}
这将创建 beanA"，而不是B".
This would create bean "A", than "B".
但是，您想要的顺序可能无法实现.你写道:
However, the order you desire may not be possible. You wrote :
A依赖于C，B依赖于A
A depends on C, B depends on A
如果 'depends on' 意味着:A 需要实例化 C，bean 必须按以下顺序创建:
If 'depends on' means : A needs C to be instantiated, the beans must be created in the following order :
- C - 因为 C 不依赖任何东西
- A - 因为 A 依赖于已经创建的 C.
- B - 因为 B 依赖于已经创建的 A.
Spring 通过分析 bean 类自动检测依赖项.
Spring automatically detects the dependencies by analyzing the bean classes.
如果 A 具有自动装配属性或类型为 C 的构造函数参数，则 spring '知道'它必须在 A 之前实例化 C.
If A has an autowired property or a constructor argument of type C, spring 'knows' that it must instantiate C before A.
在大多数情况下，这非常有效.
In most cases this works quite well.
在某些情况下，spring 无法猜测"依赖项并以不需要的顺序创建 bean.比您可以通过 @DependsOn 注释通知" spring 依赖项.Spring 将尝试相应地更改顺序.
In some cases spring cannot 'guess' the dependencies and creates beans in an unwanted order. Than you can 'inform' spring through the @DependsOn annotation about the dependency. Spring will try to change the order accordingly.
在您的情况下，如果您描述的依赖项对 spring 不可见，并且不需要依赖项来创建 bean，您可以尝试使用 @DependsOn 更改顺序:
In your case, if the dependencies you described are not visible for spring, and the dependencies are not needed to create the beans, you can try to change the order with @DependsOn :
A依赖于C，B依赖于A
A depends on C, B depends on A
可以通过
@DependsOn("C")
public class A{
...
}
@DependsOn("A")
public class B{
...
}
// C comes from another module
// and no need to annotate
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